With sweltering temperatures easing the stiffness in his chronically bad back, the defending champion birdied the final three holes Friday for a 7-under 63 and the second-round lead at Fox Chapel.

Couples, the winner last year at Westchester Country Club in Harrison, N.Y., reached 11 under on a day when the temperature reached 96 degrees with a heat index of 105.

"The heat helps," said Couples, the 1992 Masters champion. "I have some heat on my back to start the day, and then being hot and humid certainly was a good thing."

Couples has complained about stiffness all week, saying his back is sore after receiving his regular anti-inflammatory injections two weeks ago. His game hasn't shown it. Couples has one bogey through two rounds, has birdied the two par-5 holes both days and has hit 36 of 38 greens.

He birdied four of the first six holes and closed the same way, with birdies at 13, 16, 17 and 18.

"It was a great day full of a lot of good shots, but a couple long putts were made," Couples said. "Any time you're going to shoot a low round on a course that I think is like this, you're going to have to do that."

He won the Mississippi Gulf Resort Classic in March for his seventh victory on the 50-and-over tour.

Joe Daley was a stroke back after a 64. He leads the field with 16 birdies during the tournament thus far.

Dating to his previous start at the Senior PGA Championship in May, Daley is a combined 22 under in his past four rounds. He finished 66-64 (12 under) at the Senior PGA Championship to climb into a tie for fourth.

"Why not?" Daley said when asked if he went into the tournament thinking there were that many birdie opportunities available. "Why limit yourself? You have to have the right mindset."

Tom Lehman, the Regions Tradition winner in his last start, was third at 7 under after a 66. He extended his streak of consecutive rounds in the 60s to 10.

Mark Calcavecchia, coming off a victory Sunday in the Montreal Championship, was 6 under along with Bill Glasson, Michael Allen and Jay Don Blake. Calcavecchia and Blake shot 65, Glasson had a 67, and Allen a 68.

Olin Browne had a tournament-record 62 to reach 5 under. After putting 35 times in opening with a 73 Thursday, the reigning U.S. Senior Open champion drove to nearby Oakmont Country Club to work on his putting. Oakmont will host its record ninth U.S. Open in 2016.

"Obviously, that paid off a little bit," Browne said after putting 28 times in the second round.

"I got a couple good bounces. When I mis-hit a shot, it covered the bump and got up there close and I was able to take advantage of that. It was just one of those days where I hit the ball pretty well but when I didn't hit it well, I got a good bounce and it went my way."

Glasson posted his second consecutive four-birdie round of 67, and Calcavecchia made a late charge up the leaderboard by birdying the final three holes to move into a tie for fourth.

"I didn't drive particularly well, but it seemed like the holes that I missed fairways we had back pins, so it allowed me to kind of chase the ball on the greens," Glasson said. "So had they been front pins, I would have had a hard time today."

First-round leader Bruce Vaughan was 2 under. He followed a 64 with a 74 that included seven bogeys. Fred Funk, second after the first round, was 3 under after a 72.

Tom Watson also was 3 under after a 67. He's returning from a wrist injury that sidelined him since April.

Greg Norman was 1 over after a 74. He's playing his first Champions Tour event since 2009